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MPP-SOLAR LV6548

Yeah or did he mean literal binary? Like 18 ascii in binary is 10010, so 10011 would be 19 amps. I guess that could be what he meant by a bit more hehe...


Anyways, I'm curious what he replies back with. Thanks for inquiring on it. I'm just concerned at why MPP may not put built-in logic in the MPPT hardware or firmware to prevent it from pulling more current than it could even handle (to where it could fry itself).

For example, on Sol-Ark 12k specs sheet, they explicitly say: 'Self-Limiting' I guess price plays a role too...

View attachment 79149

MPPT algorithm dictates that the sweep and control circuit, has precise control of the amps, by altering the charger load (by decreasing resistance on the PV circuit), could pull the voltage down (only as far as it needs to), drawing amps up to some predefined maximum, and stop it from going beyond that point which it can no longer safely handle.

I would like MPP to clarify how their MPPT controller logic functions.

I'm not worried about it myself on my LV6548's because I'm not approaching any of the limits. But it is useful to know how this inverter behaves when it comes to helping others out. If they don't have protections in place to safeguard from over-paneling, then we ought to know about it.
I'll chalk this up, likely, to poor comms ... in that the manual should say, "Self-limiting" AND the technical support reps should be well trained on this. Given the Amperages of most of the panels I've seen today, it's the only thing that makes sense. I've seen this a million times with highly technical products ...
 
Max allowed PV Power: 6500W/6500W
MPPT range: 150 ~425V
So the Max DC Voltage spec is:
500V@18A (9000W), 450V@20A (9000W)
Max DC Current (per MPPT) is self limiting:
400V@18A (7200W), 300V@20A (6000W)

So if you have lets say 200V from panel instead of 300V, to get 6000W then the current will have to be 30A, if that is the case then you will never going to get 6000W if your PV is not at 300V, so it seems that you need to get the PV Voltage to be higher than 300V so you will not exceed the 20A limit.
Am I correct? I wonder why it has MPPT range down to 150V.
If you’re talking about the LV6548, is limited to 250v…
 
If you’re talking about the LV6548, is limited to 250v…

Well we know the Voc limitation, that is well documented (that you should never exceed that ever), it is the max amperage, does it have the ability to destroy itself (when one over-panels) and pull up the amps beyond it's max amp published spec? Or is it self-limiting like a Sol-Ark?
 
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Sol-Ark 12k specs sheet post #359.
Max allowed PV Power: 6500W/6500W
MPPT range: 150 ~425V
So the Max DC Voltage spec is:
500V@18A (9000W), 450V@20A (9000W)
Max DC Current (per MPPT) is self limiting:
400V@18A (7200W), 300V@20A (6000W)

So if you have lets say 200V from panel instead of 300V, to get 6000W then the current will have to be 30A, if that is the case then you will never going to get 6000W if your PV is not at 300V, so it seems that you need to get the PV Voltage to be higher than 300V so you will not exceed the 20A limit.
Am I correct? I wonder why it has MPPT range down to 150V.

My take on this, is those numbers are just representative of some lab spec 'snapshot' they came up with in their lab testing (based on some common solar panel load), perhaps to be taken somewhat with a grain of salt. We would have to ask Sol-Ark to explain if we really wanted to know for sure (otherwise I'm purely speculating).

My thought is they must have some logic built into their MPPT sweeping, that first senses the open Voc on a 'loose' circuit (no load), to see what the Voc is at, create some kind of a map on what the max current might be, start MPPT sweep, drawing the voltage down with battery charger load (drawing up the amperage), then usually in my mind, they would have some type of watts calculation, where they establish a maximum amps (so long as it doesn't go over a hard maximum current). They could even use temperature sensing on the transistors or something to help determine how much current they could safely draw staying under a maximum temp. Sometimes, max current depends on temperature and if we can keep the chips cool enough.

We also know that different panels have different MPPT curves, and with different wiring schemes, it seems we can't understand what those numbers mean in the real world. We only know that they give a PV Voc max voltage spec, claim they are 'self-limiting' on DC amps, so we can assume that they won't ever pull higher current and put itself into a situation where it could fry itself supposedly.

Again, that is pure speculation, we wouldn't know for sure unless Sol-Ark rep could explain.
 
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Notes from 150/60 spec sheet:
Page 50:
9.5.1.
PV reverse current too high Overcurrent does not necessarily damage the solar charger, but it will cause damage if the array produces too much current while, at the same time, the array has been connected in reverse polarity to the solar charger. Damage due to overcurrent is not covered under warranty. Refer to the solar chargers technical specifications for the maximum PV short circuit power current rating.
Page 56/57

1a) The solar charger will limit input power if more PV power is connected.

1b) The PV voltage must exceed Vbat + 5V for the controller to start. Thereafter the minimum PV voltage is Vbat + 1V.
2) A higher short circuit current may damage the solar charger in case of reverse polarity connection of the PV array.
3) Equalization is by default disabled.
4) For more information on data communication see the data communication paper in the Technical information section on our website.
5) MC4 models: several splitter pairs may be needed to parallel the strings of solar panels. Maximum current per MC4 connector is 30A. The MC4 connectors are internally parallel connected to a single MPPT tracker.
https://www.victronenergy.com/uploa...0-60__150-70/MPPT_solar_charger_manual-en.pdf

See my post #7, Victron shows max input current rating but that is based on if faulty connection is made.
So I sure like to know how other SCC comes up with the max input current rating, hopefully we get some answer from Sol-Ark, and other SCC maker.
 
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Notes from 150/60 spec sheet:
Page 50:
9.5.1.
PV reverse current too high Overcurrent does not necessarily damage the solar charger, but it will cause damage if the array produces too much current while, at the same time, the array has been connected in reverse polarity to the solar charger. Damage due to overcurrent is not covered under warranty. Refer to the solar chargers technical specifications for the maximum PV short circuit power current rating.
Page 56/57

1a) The solar charger will limit input power if more PV power is connected.

1b) The PV voltage must exceed Vbat + 5V for the controller to start. Thereafter the minimum PV voltage is Vbat + 1V.
2) A higher short circuit current may damage the solar charger in case of reverse polarity connection of the PV array.
3) Equalization is by default disabled.
4) For more information on data communication see the data communication paper in the Technical information section on our website.
5) MC4 models: several splitter pairs may be needed to parallel the strings of solar panels. Maximum current per MC4 connector is 30A. The MC4 connectors are internally parallel connected to a single MPPT tracker.
https://www.victronenergy.com/uploa...0-60__150-70/MPPT_solar_charger_manual-en.pdf

See my post #7, Victron shows max input current rating but that is based on if faulty connection is made.
So I sure like to know how other SCC comes up with the max input current rating, hopefully we get some answer from Sol-Ark, and other SCC maker.

Yeah, for me it's more of an issue where I'd like to know how various SCC's handle it, for the purpose of giving good advice to people considering to over-panel. Will likely keep saying, proceed at your own risk, contact the manufacturer to be certain for your specific case (since there are too many brands/models to keep a database on).

I'm aware of Victron's stance, I have a 250|100 and I've read that same section in the manual too, they imply is fine to over-panel, as it won't draw more than it can safely handle, but with MPP, it seems we don't know for sure. The other issue is, say MPP came back and said it was fine on a particular MPP model, that doesn't mean all MPP inverter models are the same, we know some of these companies use rebranded equipment from different manufacturers and products within their own lines may have different behaviors based on what branches they come from...

Me personally, I just won't exceed max Voc and max amps of the controller, and if I need more panels, I will just stack more inverters to get more PV inputs. It does cost more, but gives more redundancy and I could run even bigger equipment in my shop and stuff, that is why it is important to me to use stackable inverters so the system can scale out when you hit limits and want to grow it more. Plus your less likely to waste watts when you don't over-panel.

And in the meantime, I'll make it a point to not wire the PV inputs backwards. :geek:
 
I found the video on the LV6548, it looks like it will clip the current to around 18A, see time stamp @12:59 and on, very interesting.
 
I found the video on the LV6548, it looks like it will clip the current to around 18A, see time stamp @12:59 and on, very interesting.

Yeah, nice video. It just goes to show that just because it is rated at 18a max, doesn't mean that is where it will calculate maximum power point. It seems 17a in his current case was where it would pull the maximum watts based on where his voltage was. I guess some of it depends on how much demand was on it too at the time, like loads and battery charging.

MPPT charger is just a big fancy buck converter, trying to figure out how to pull the most watts off the panels at any time it needs it, by manipulating the load/resistance on the circuit to have an effect on volts vs amps to find the most watts (hopefully designed well enough to not blow itself up).
 
So does it mean that you can over panel and it will just limit the input current to 18A?
 
So does it mean that you can over panel and it will just limit the input current to 18A?

I don't know, if I had too much money laying around I could test it, over-panel to some decent amount, wait til full-Sun season, drain the batteries down a decent amount so the charger will charge good, run some good AC loads, do tests like that for like a month, study the charts, I don't know.

Or like Scott is trying to do, try to get some confirmation/clarification from the manufacturer.

But yeah it's true, maximum power point isn't found at max amps on a solar circuit, it does the periodic MPPT sweep, pulls down volts and amps comes up to some high point, and it calculates the best watts (amps x volts) along the curve, and holds it there (for some time until it triggers another MPPT sweep based on a schedule programmed in the firmware), which may not be where the amps is at its highest (since as the amps rises, the voltage is coming down on some other curve).

1641882507101.png

The question might be, how much you over-panel? If you over-panel by a significant amount, will the controller know to stop on its high amp limit when it finds maximum power point (and it happens to be higher than max amps limit)? Or when doing an MPPT sweep can it exceed the limit for a time? Or does it have safeguards to protect itself from over-current?

How much was that guy in the You Tube video (DMI Inc) over-paneled, did he say? I only watched that last part, might have to watch the rest tomorrow. Perhaps we could ask him more questions...
 
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I guess some of it depends on how much demand was on it too at the time, like loads and battery charging.

This right here is how I see how you fry the unit. In the case of kromc5, my thoughts are the LV6548 can run batteryless, which means the PV input can be directly diverted to the inverter. What occurs is the unit will draw as many amps as available in the case of high loads from PV if needed. This is advantageous for starting loads that might only have a surge for a few seconds, quite another matter when you have high constant loads and the unit is passing PV amps thru to the inverter.
 
I found the video on the LV6548, it looks like it will clip the current to around 18A, see time stamp @12:59 and on, very interesting.
I'm familiar with his setup, I've watched his videos before. While the string might produce 18A, you have to remember the voltage of his array string is around 200V. That comes to around 3600w. He only uses 1 SCC per unit, the SCC in each unit is rated for 4000w, for a total of 8000w which is what the unit is rated for. The unit isn't really clipping amps, it is simply using the available watts per string and adjusting the voltage for what is available.

When he planned his system, he designed the PV strings to be below the 4Kw max per string. He is not over paneling the units. If you watch the first few minutes of the video, he describes the size of each string, the strings are all under 4Kw each. This is important, you want to get the VOC up to the recommended range around the 190V to 230V range and the full wattage of the string under 4Kw.

He actually might be better off using both SCC's in each unit, you simply Y off the single wire and split the amps to each SCC in the unit. This would lessen the heat generated on each SCC leading to extended lifespan. Heat kills electronics.
 
Yeah, for me it's more of an issue where I'd like to know how various SCC's handle it, for the purpose of giving good advice to people considering to over-panel. Will likely keep saying, proceed at your own risk, contact the manufacturer to be certain for your specific case (since there are too many brands/models to keep a database on).

I'm aware of Victron's stance, I have a 250|100 and I've read that same section in the manual too, they imply is fine to over-panel, as it won't draw more than it can safely handle, but with MPP, it seems we don't know for sure. The other issue is, say MPP came back and said it was fine on a particular MPP model, that doesn't mean all MPP inverter models are the same, we know some of these companies use rebranded equipment from different manufacturers and products within their own lines may have different behaviors based on what branches they come from...

Me personally, I just won't exceed max Voc and max amps of the controller, and if I need more panels, I will just stack more inverters to get more PV inputs. It does cost more, but gives more redundancy and I could run even bigger equipment in my shop and stuff, that is why it is important to me to use stackable inverters so the system can scale out when you hit limits and want to grow it more. Plus your less likely to waste watts when you don't over-panel.

And in the meantime, I'll make it a point to not wire the PV inputs backwards. :geek:
For me, I'd have to add on TWO more 6548 Inverters for split phase, or rewire my house. Plus, I have PLENTY of power going from the Inverters to my house and batteries ... this 18A per PV input limit is quite ridiculous as compared to everything else these boxes can handle. MPP Solar hasn't responded yet ...
 
For me, I'd have to add on TWO more 6548 Inverters for split phase, or rewire my house. Plus, I have PLENTY of power going from the Inverters to my house and batteries ... this 18A per PV input limit is quite ridiculous as compared to everything else these boxes can handle. MPP Solar hasn't responded yet ...

You shouldn't have to rewire the house if you had to move to 4-inverter split-phase topology. The LV6548's are stackable up to 3x for L1 and 3x for L2, you would still only have one single split-phase output going to your main AC panel, when using four LV6548s.

1641911938351.png

You would have higher idle draw with 4 inverters though, presumably not an issue if you have more solar panels I suppose.

You could also just add some more standalone charge controllers if you don't need more inverter capacity, but I don't see a problem really just to have too much inverter, as they would be working at lower duty cycle and probably allow them to last longer lifespan being under less load.

Hopefully MPP will respond soon with some promising info though...
 
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This right here is how I see how you fry the unit. In the case of kromc5, my thoughts are the LV6548 can run batteryless, which means the PV input can be directly diverted to the inverter. What occurs is the unit will draw as many amps as available in the case of high loads from PV if needed. This is advantageous for starting loads that might only have a surge for a few seconds, quite another matter when you have high constant loads and the unit is passing PV amps thru to the inverter.

Yeah, I totally agree with what you're saying... I just think that is more of a product bug, that some of the manufacturers have worked out while others have not. If I was a manufacturer, I would include this safeguard (circuit protection) in all my products, so I could keep potential warranty repairs down.

Or at least these manufacturers ought to be much more clear in their documentation about how going over watts will be handled by the hardware.
At least if they could put a clear message in there like Victron or Sol-Ark does.

Victron: "The solar charger will limit input power if more PV power is connected."
Sol-Ark: "Max DC current per MPPT (self limiting)"

Or else a big warning, saying:
WARNING: Over-paneling on watts or amps will damage the unit. Please design your solar system PV circuits to keep watts and amps under rated maximums!

(One problem is some of these messages get lost in document translations to English)

They always seem to be clear about not going over on max PV input Voc...

I also personally don't see running batteryless to be a best practice in my eyes anyways. I think that was more of a thing the manufacturers added to fill a market demand, but even if I didn't want battery capacity, I'd still just install some small batteries on a system to help it with surge demands. Batteryless is a practically useless feature anyways, as it only works on single inverter mode.

Anyways, it is what it is I guess. Perhaps things will evolve more, going into the future...
 
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You shouldn't have to rewire the house if you had to move to 4-inverter split-phase topology. The LV6548's are stackable up to 3x for L1 and 3x for L2, you would still only have one single split-phase output going to your main AC panel, when using four LV6548s.

View attachment 79193

You would have higher idle draw with 4 inverters though, presumably not an issue if you have more solar panels I suppose.

You could also just add some more standalone charge controllers if you don't need more inverter capacity, but I don't see a problem really just to have too much inverter, as they would be working at lower duty cycle and probably allow them to last longer lifespan being under less load.

Hopefully MPP will respond soon with some promising info though...
I'd have to go to four to NOT rewire ... with three I'd need to rewire: two used for single phase 120V, the third for 240V appliances (I think - I haven't done the load calcs), which means I'd have to basically pull apart my main panel and separate the two systems. Trying not to spend an extra $3K (or $1.5K if I can even find another one right now), nor do all the rewiring work ...
 
Here's the latest ... I cc'd Jason at SanTan solar on my note to MPP Solar, and here was his response, as well as mine (nothing back from MPP Solar):

Hi Scott,

I received the following response from MPP last February when I asked.

“For LV 6548 . please note the PV max input current can be 2 panels in parallel. having the max input under 22A , it will all be fine.

I understand a 18A limit is too low and we have done a series test to confirm under 22A will be fine”.

Not sure if you can go over 22A. I suspect you will be fine. I am have not heard of any issues from previous customers.

Thanks

Jason

SanTan Solar

And here was my response to him:

Cool, thanks Jason. That number is all over the place (Ian at a US competitor of yours, according to the forum, said 23A) ... given how close I am to the edge of the range, I'd be quite hesitant to move forward if my panels weren't SW & SE, instead of due South and at 10 degrees off optimal during the summer.
 
He actually might be better off using both SCC's in each unit, you simply Y off the single wire and split the amps to each SCC in the unit. This would lessen the heat generated on each SCC leading to extended lifespan. Heat kills electronics.
is it that simple? makes sense intuitively but Is there a risk of the two mppts getting into a conflict?
 
For me, I'd have to add on TWO more 6548 Inverters for split phase, or rewire my house. Plus, I have PLENTY of power going from the Inverters to my house and batteries ... this 18A per PV input limit is quite ridiculous as compared to everything else these boxes can handle. MPP Solar hasn't responded yet ...
Not following what you mean here. You only need 2 LV6548 for split phase operation.

As for the 18A limit, you can do that per PV input. There are 2 PV inputs per LV6548. That's 36A per unit, times 2 units is 72A. Let's say you source 300W panels, VOC is 40V and ISC is 9.5A. You could go 5S2P and that is 3000W per string, times 4 strings, 12Kw for the total array.

The idea is to hit the sweet spot where VOC is up to 230V yet amps are around the 18A.

If you need more PV capacity, you can just add standalone SCC's, as many as you want. It won't make a difference to the LV6548's. The reason some will use 4 LV6548's is to reduce overall load on the units instead of running them near capacity 100% of the time.
 
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